Hydrogenation of catmint oil

ABSTRACT

Disclosed are methods for treating catmint oil. The treated catmint oil can be used for the production of hydrogenated catmint oil, which is enriched in the insect repellent, dihydronepetalactone.

This application claims the benefit of U.S. Provisional Application No.60/876,569, filed 21 Dec. 2006, which is incorporated in its entirety asa part hereof for all purposes.

TECHNICAL FIELD

The present invention relates to the hydrogenation of the essential oilof the catmint plant, Nepeta cateria. The hydrogenation of the essentialoil provides an enriched source of the insect repellent,dihydronepetalactone.

BACKGROUND

Dihydronepetalactone (DHN) has been shown to be an effective insectrepellent, as discussed in U.S. Ser. No. 05/112,166.Dihydronepetalactone can be produced by hydrogenating nepetalactone, acomponent of the essential oil from the catmint plant, Nepeta cataria(herein referred to as catmint oil). Catmint oil can be purified fromplants of the N. cataria by various isolation processes including steamdistillation [Regnier, F. E. et al, Phytochemistry (1967) 6:1281-1289],organic solvent extraction, microwave-assisted organic solventextraction, supercritical fluid extraction, mechanical extraction andenfleurage (initial cold extraction into fats followed by organicsolvent extraction). The catmint oil so obtained can be used in thecrude form to produce DHN, however the hydrogenation reaction can beadversely affected by undesirable components contaminating the crudecatmint oil.

Nepetalactone has been purified from catmint oil by crystallization[Regnier, F. E. et al, Phytochemistry (1967) 6:1271-1280], howevercrystallization is expensive, and on the potential scale required forcommercialization, it is uneconomical. Therefore, it would be highlydesirable to produce a catmint oil with improved properties, such thathigh yields of the insect repellent DHN may be produced.

SUMMARY

In one embodiment, the processes of this invention provide a process forpreparing hydrogenated catmint oil by (a) distilling a beginning amountof crude catmint oil to produce (i) a distillate fraction comprisingvolatile components driven off from the crude catmint oil, wherein theweight of the distillate fraction comprises about 2% to about 20% of theweight of the beginning amount of crude catmint oil, and (ii) a potfraction; (b) contacting the pot fraction produced in step (a) withhydrogen and a hydrogenation catalyst to produce hydrogenated catmintoil; and (c) optionally, recovering the hydrogenated catmint oil of step(b).

In another embodiment, the processes of this invention provide a processfor preparing hydrogenated catmint oil by (a) distilling a beginningamount of crude catmint oil that has at least about 150 ppm ofsulfur-containing compounds to produce (i) a distillate fraction thatcomprises at least about 8 wt % of the amount of sulfur-containingcompounds, in the beginning amount of crude catmint oil, and (ii) a potfraction; (b) contacting the pot fraction produced in step (a) withhydrogen and a hydrogenation catalyst to produce hydrogenated catmintoil; and (c) optionally, recovering the hydrogenated catmint oil of step(b).

In a further embodiment, the processes of this invention provide aprocess for preparing hydrogenated catmint oil by (a) contacting crudecatmint oil with an oxidizing agent to produce a first treated catmintoil; (b) separating the first treated catmint oil from the oxidizingagent to produce a second treated catmint oil; (c) contacting the secondtreated catmint oil with hydrogen and a hydrogenation catalyst toproduce hydrogenated catmint oil; and (d) optionally recovering thehydrogenated catmint oil.

DETAILED DESCRIPTION

This invention relates to methods for treating the essential oil of thecatmint plant, Nepeta cataria, herein referred to as catmint oil. Thetreated catmint oil so produced can be used in a hydrogenation reactionto produce hydrogenated catmint oil, which is enriched in the insectrepellent, dihydronepetalactone. Methods for treating catmint oilinclude distillation and/or treatment with an oxidizing agent.

Definitions

In the description of the processes hereof, the following definitionalstructure is provided for certain terminology as employed in variouslocations in the specification:

The term “nepetalactone” as used herein refers to the compound havingthe general structure of Formula I:

The term “dihydronepetalactone” (“DHN”) as used herein refers to thecompound having the general structure of Formula II:

The term “puleganic acid” as used herein refers to the compound havingthe general structure of Formula III:

The term “nepetalic acid” as used herein refers to the compound havingthe general structure of Formula. IV:

The term “crude catmint oil” as used herein refers to catmint oil thathas been obtained from the catmint plant, N. cataria, and containspredominantly the trans-cis and/or cis-trans isomers of nepetalactone asshown in Formulae V and VI, respectively.

Crude catmint oil may also contain extraneous components such ascaryophyllenes, carvones, limonenes and other sesquiterpenes, and otherunidentified impurities. One or more of these extraneous components candecrease the effectiveness of the hydrogenation of catmint oil, asmeasured for example by the rate of conversion of the nepetalactonetherein to dihydronepetalactone. The processes of this invention canassist with the removal of one or more of the extraneous components,thereby improving the hydrogenation of catmint oil.

In one embodiment, a process is provided herein for preparinghydrogenated catmint oil by (a) distilling a beginning amount of crudecatmint oil to produce (i) a distillate fraction comprising volatilecomponents driven off from the crude catmint oil, wherein the weight ofthe distillate fraction comprises about 2% to about 20% of the weight ofthe beginning amount of crude catmint oil, and (ii) a pot fraction; (b)contacting the pot fraction produced in step (a) with hydrogen and ahydrogenation catalyst to produce hydrogenated catmint oil; and (c)optionally, recovering the hydrogenated catmint oil of step (b).

In another embodiment the distillate fraction has about 5% to about 10%by weight of the beginning amount of crude catmint oil.

Depending on the process used to obtain catmint oil from N. cataria, theextraneous components contained in catmint oil can comprisesulfur-containing compounds, dimethyl sulfide for example, that maydecrease the rate of conversion of nepetalactone, possibly by poisoningthe hydrogenation catalyst. Sulfur-containing compounds present in thecrude catmint oil can be quantitated using X-ray fluorescencespectroscopy.

In another embodiment, a process is provide herein for preparinghydrogenated catmint oil by (a) distilling a beginning amount of crudecatmint oil that has at least about 150 ppm of sulfur-containingcompounds to produce (i) a distillate fraction that comprises at leastabout 8 wt % of the amount of sulfur-containing compounds in thebeginning amount of crude catmint oil, and (ii) a pot fraction; (b)contacting the pot fraction produced in step (a) with hydrogen and ahydrogenation catalyst to produce hydrogenated catmint oil; and (c)optionally, recovering the hydrogenated catmint oil of step (b).

In more specific embodiments, the distillate fraction of step (a)comprises at least about 25%, at least about 50% or at least about 75%of the sulfur-containing compounds by weight relative to the beginningamount of sulfur-containing compounds in the crude catmint oil.

Distillation is a well-known process [see, for example, Seader et al,“Distillation”, in Perry's Chemical Engineers' Handbook, 7^(th) Ed.(1997) McGraw-Hill, Section 13]. Distillation methods suitable for thecurrent process include vacuum distillation, steam distillation andsolvent distillation. Both steam and solvent distillation can optionallybe performed under vacuum. Distillation of crude catmint oil can becarried out using any suitable apparatus, such as a pot or resin kettleoutfitted with a heating element, a shell and tube condenser, and a dryice finger. The temperature at which distillation and condensation occurwill depend on the process used. For example, the heating temperaturewill be lower when vacuum is applied during the distillation process.

When steam distillation is utilized, approximately 2% to about 40% water(by weight relative to the weight of the catmint oil plus the water) maybe added to the catmint oil. In a more specific embodiment,approximately 5% to about 20% water (by weight relative to the weight ofthe catmint oil plus the water) may be added to the catmint oil. In oneembodiment, the mixture of catmint oil and water can be distilled at atemperature of about 100° C., i.e. the boiling point of the water, atatmospheric pressure. In an alternative embodiment, the distillation canbe performed at an absolute pressure of less than or equal to about 68.9kPa. In yet another embodiment, the distillation can be performed at anabsolute pressure of less than or equal to about 41.4 kPa. At lowerpressures, the distillation temperature will be lower due to the lowerboiling point of water at reduced pressure.

Solvent distillation refers to a distillation process whereby a solventis added to aid in the separation of components of close-boilingmixtures. “Close-boiling” mixtures are mixtures wherein the boilingpoints of the components are similar. In this invention, the solventused is typically more volatile than the catmint oil, and when distilledoff, removes some of the volatile species present in the crude oil.Preferably the solvent is a compound that is inert to the catmint oil.Solvents suitable for this invention include C₁ to C₅ straight-chain orbranched alcohols. In one embodiment, the solvent is an alcohol selectedfrom the group consisting of methanol, ethanol, isopropanol andn-propanol.

Preferably, the initial solvent concentration is from about 5% to about60% by weight relative to the combined weight of the catmint oil plusthe solvent. In another embodiment, the initial solvent concentration isfrom about 10% to about 25% by weight relative to the combined weight ofthe catmint oil plus the solvent. Solvent distillation can be performedat atmospheric pressure. In an alternative embodiment, the distillationis performed at an absolute pressure of less than or equal to about 68.9kPa. In yet another embodiment, the distillation is performed at anabsolute pressure of less than or equal to about 41.4 kPa. Thetemperature at which solvent distillation is carried out will depend onparameters such as the solvent used, the concentration of the solvent,and the pressure at which the distillation is carried out. Typicaltemperatures range from about 50° C. to about 100° C.

In a further embodiment of this invention, solvent distillation can becombined with steam distillation. For example, one could carry out steamdistillation of crude catmint oil as described above to obtain a catmintoil from which some of the volatile components and most of the waterhave been removed. In a second distillation step, this steam distilledcatmint oil is then contacted with a solvent, and solvent distillationis performed as described above. Solvent distillation will removeadditional volatile components not removed by steam distillation. Inaddition, solvent distillation can be used to remove residual waterintroduced into the catmint oil during steam distillation.

At temperatures above about 80° C., nepetalactone isomers in wet catmintoil may hydrolyze to undesirable products, such as nepetalic acid. Therate of hydrolysis increases with temperature up to about 200° C., wherethe catmint oil thermally degrades. Therefore, it would be desirable tobe able to carry out the distillation of catmint oil at a lowertemperature to avoid the hydrolysis of nepetalactone. The temperaturecan be reduced by operating the distillation apparatus under vacuum. Theamount of vacuum applied to the system will depend on the systemcomponents, however achieving a vacuum of less than about 68.9 kPa(absolute) is preferred. In one embodiment, vacuum distillation isperformed at an absolute pressure of less than about 6.89 kPa.

In an alternative to distillation, a process is provided herein forpreparing hydrogenated catmint oil by (a) contacting crude catmint oilwith an oxidizing agent to produce a first treated catmint oil; (b)separating the first treated Catmint oil from the oxidizing agent toproduce a second treated catmint oil; (c) contacting the second treatedcatmint oil with hydrogen and a hydrogenation catalyst to producehydrogenated catmint oil; and (d) optionally recovering the hydrogenatedcatmint oil.

Examples of oxidizing agents suitable for use herein to contact withcrude catmint oil include Na₂B₄O₇.10H₂O, which is available for examplein a product such as 20 Mule Team® Borax. In one embodiment, contactingcan occur by mixing the catmint oil with Na₂B₄O₇.10H₂O, followed byfiltering the mixture to separate the Na₂B₄O₇.10H₂O from the oxidizedcatmint oil. In an alternative embodiment, the Na₂B₄O₇.10H₂O can beplaced in a, column, and the crude catmint oil can be drained throughthe column. Na₂B₄O₇.10H₂O can be used at a concentration of about 1% toabout 50% by weight relative to the combined weight of Na₂B₄O₇.10H₂Oplus the catmint oil. In more specific embodiments, Na₂B₄O₇.10H₂O can beused at concentrations of about 3% to about 50% and about 15% to about50% by weight relative to the combined weight of the Na₂B₄O₇.10H₂O plusthe catmint oil.

Other suitable oxidizing agents for use to contact with crude catmintoil include a hydrogen peroxide solution, which can be used at aconcentration of about 1% to about 15% relative to the combined weightof the hydrogen peroxide solution plus the catmint oil. A 30% hydrogenperoxide solution has been found suitable. The mixture of hydrogenperoxide and catmint oil are vigorously agitated, and the aqueoushydrogen peroxide phase is allowed to separate from the organic catmintoil phase. The catmint oil phase can be recovered from the aqueoushydrogen peroxide phase by decantation. Contacting of crude catmint oilwith Na₂B₄O₇.10H₂O or a dilute hydrogen peroxide solution can beperformed at room temperature (about 25° C.).

Ozone is yet another alternative oxidizing agent, which can be used byvigorously agitating the crude catmint oil in the presence of ozone.

In further alternative embodiments, a step of contacting crude catmintoil with an oxidizing agent can be performed before a step ofdistillation, as described above, is performed.

Crude catmint oil can be obtained from a supplier such as George ThackerSons (Alberta, Canada), or can be obtained from catmint plant materialby known methods, such as distillation [Regnier, F. E. et al,Phytochemistry(1967) 6:1281-1289]. One particular method for obtainingcatmint oil suitable for use herein includes the steps of (a) contactingNepeta cataria plant material with steam to form a volatilized mixturecomprising catmint oil and water; (b) condensing the volatilized mixtureformed in step (a) to form a liquid mixture comprising catmint oil andwater in which catmint oil is dissolved in water; (c) contacting theliquid mixture formed in step (b) with salt to provide a mixture inwhich catmint oil and salt are both dissolved in water, and in which

-   -   (i) the solubility of catmint oil in the solution of water and        salt is at least about 50% less than the solubility of catmint        oil in water, and/or    -   (ii) the ratio        [(ρ_(catmint oil)−ρ_(aqueous solution))/μ_(aqueous solution)]        where ρ is density, μ is viscosity and the aqueous solution is        the solution of water and salt, is less than or equal to about        −0.05,        to provide in the mixture a catmint oil phase that is separated        from an aqueous salt solution phase; and (d) recovering the        catmint oil phase.

According to this method, plant material is packed into a retort. Thelid of the retort is closed and sealed to both the retort and to acondenser. Steam for the distillation of the catmint plant material canbe provided by any suitable means. In one embodiment steam is providedto the retort by direct injection through an injection manifold. In analternative embodiment, the steam can be obtained by adding water to theretort, and boiling the water in the presence of the plant material. Thelatter method is referred to as using a direct fired retort.

The volatized oil that is produced when steam contacts the plantmaterial is ducted, along with the steam, to a condenser. Cooling water,from any suitable water source, flows through the condenser. Its coolingeffect allows the steam and catmint oil vapor to condense to form theheterogeneous liquid condensed mixture. The condenser is configured insuch a way as to allow gravity to drain the condensed water and catmintoil out of the condenser and into a collection can. The water andcatmint oil are ducted into the collection can optionally using internalbaffles in such a way as to produce a quiescent zone to allow the oiland water to effectively separate. Typically, the temperature of thecondensate is controlled at a modest temperature, approximately 40-60°C., to allow the oil and water to effectively separate in the quiescentzone of the separation can.

The heterogeneous liquid condensed mixture comprising catmint oil andwater can then be contacted with salt, such as by allowing the entiremixture to come into contact with salt. In one embodiment, a porousmaterial such as burlap, filter paper, filter cloth (such ascheesecloth), pr a fine mesh screen, is placed in a funnel, and the saltis placed on the porous material. The heterogeneous mixture contacts thesalt, and flows through the funnel into the collection can. The additionof salt causes the heterogeneous liquid condensed mixture to separateinto a catmint oil phase (top phase in the collection can) and anaqueous salt solution phase (bottom phase in the collection can). Thecatmint oil phase can be recovered by decantation of the top phase.Salts that are suitable for the process include the sulfate, nitrate andphosphate salts of Groups 1 and 2 of the Periodic Table of the Elements.

This method also provides a method for reducing the amount of catmintoil in wastewater by recycling the condensed water phase back to theretort. This method, with or without recycling, can be carried out undervacuum. Vacuum provides the advantage of allowing the distillationprocess to be operated under reduced temperature. The amount of vacuumapplied to the system will depend on the system components, howeverachieving an absolute pressure of about 70 kPa to about 13 kPa ispreferred.

Following distillation and/or contact with an oxidizing agent, the potfraction containing catmint oil, or the second treated catmint oil, asdescribed above, can be used in a hydrogenation reaction to obtainhydrogenated catmint oil. The hydrogenation reaction may be carried outin the presence of hydrogen at a temperature of about −10° C. to about200° C. The hydrogen pressure for the reaction is generally from about0.1 MPa to about 20.7 MPa. The time, temperature, hydrogen pressure andflow rate and feed may be adjusted, according to known principles, toobtain optimal conversion of hydrogenation of catmint oil using a givencatalyst. A suitable hydrogenation reaction is that which is describedin U.S. Pat. No. 7,067,677 (which is incorporated in its entirety as apart hereof for all purposes). Described therein is the hydrogenation ofnepetalactone in the presence of a catalytic metal that is not nickel,platinum or palladium. The process can be carried out at a temperatureof about 25° C. to about 250° C. at a hydrogen pressure of about 0.1 MPato about 20 MPa.

Other suitable processes for making a dihydronepetalactone include aprocess of (a) contacting, optionally in the presence of a solvent, amixture comprising trans-cis nepetalactone and cis-trans nepetalactonewith at least one first solid hydrogenation catalyst and hydrogen at afirst temperature or temperatures until the concentration of trans-cisnepetalactone is reduced by at least 50% by weight of the weight of thetrans-cis nepetalactone at the start of the reaction to form a firstproduct mixture; (b) optionally separating the first product mixturefrom the at least one first solid hydrogenation catalyst to form aseparated first product mixture; (c) contacting the first productmixture or separated first product mixture with at least one secondsolid hydrogenation catalyst and hydrogen at a second temperature ortemperatures to form a second product mixture; and (d) separating saidsecond product mixture from step (c) from the at least one first solidhydrogenation catalyst and/or the at least one second solidhydrogenation catalyst. The at least one first solid hydrogenationcatalyst and said at least one second solid hydrogenation catalyst areindependently selected and comprise catalytic metal selected fromelements from the group consisting of iron, ruthenium, rhenium, copper,osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, alloys orcompounds thereof; and combinations thereof. In one embodiment, step (a)is performed at a temperature or temperatures of from about 0° C. toabout 100° C. In another embodiment, step (c) is performed at atemperature or temperatures of from about 50° C. to about 150° C.

The hydrogenation reaction may be carried out in batch in a singlereactor, in sequential batch in a series of reactors, in reaction zoneswithin one or more reactors, or in continuous mode in any of theequipment customarily employed for continuous processes.

Following the hydrogenation reaction, the hydrogenated catmint oil canbe recovered from the reaction mixture by known methods of separation,such as decantation or filtration. Dihydronepetalactone can be recoveredfrom the hydrogenated catmint oil, for example, by columnchromatography.

The advantageous attributes and effects of the processes hereof may beseen in a series of examples, as described below. The embodiments ofthese processes on which the examples are based are representative only,and the selection of those embodiments to illustrate the invention doesnot indicate that materials, conditions, arrangements, approaches,reactants, steps or techniques not described in these examples are notsuitable for practicing these processes, or that subject matter notdescribed in these examples is excluded from the scope of the appendedclaims and equivalents thereof.

EXAMPLES

The following abbreviations are used: GC is gas chromatography; GC-MS isgas chromatography-mass spectrometry; FID is flame ionization detector;NMR is nuclear magnetic resonance; ° C. is degrees Centrigrade; MPa ismega Pascal; kPa is kilo Pascal; Pa is Pascal; rpm is revolutions perminute; mL is milliliter; CMO is catmint oil; wt % is weight percent;TOS is time on stream; NPL is nepetalactone; DHN isdihydronepetalactone; h is hour; conc. is concentration; conv. isconversion; temp. is temperature; ° C. is degrees Centigrade; kg iskilogram; XRF is X-ray fluorescence spectroscopy; ppm is parts permillion.

Catmint oil, which was extracted by steam distillation of herbaceousmaterial from the catmint Nepeta cataria, was obtained from GeorgeThacker Sons (Alberta, Canada). Ethanol, hexanes and isopropanol, sodiumchloride, and hydrogen peroxide were obtained from Sigma-Aldrich (St.Louis, Mo.). 20 Mule Team® Borax (Na₂B₄O₇.10H₂O) was obtained from agrocery store, however Na₂B₄O₇.10H₂O is available from Sigma-Aldrich.The catalyst ESCAT 142 (5% Pd/C) was obtained from Engelhard Corp.(Iselin, N.J.).

Determination of Catmint Oil Constituents and the Hydrogenated CompoundsThereof

Samples were diluted with an internal standard solution and injected ona DB FFAP column using an HP5890 (Agilent Technologies, Palo Alto,Calif.) GC equipped with a FID detector. The injection and detectortemperatures were 250° C. The temperature of the column was linearlyramped from 50° C. to 250° C. for 20 min and held at 250° C. for theduration of the run. A split mode inlet was used. Peak identificationand relative response factors of the major components were determinedusing calibration standards of nepetalactone, dihydronepetalactone,puleganic acid and nepetalic acid.

Determination of Sulfur Content

Sulfur was quantitated using X-ray fluorescence spectroscopy (XRF)(Panalytical model 2400 wavelength dispersive XRF system (PanalyticalInc., Tempe, Ariz.)).

Hydrogenation Reactions

The rate of hydrogenation was measured by conducting a small scale testhydrogenation reaction in a 50 mL stirred batch autoclave reactorcharged with a solution of catmint oil and a powdered catalyst, asdescribed below. The reactor was sealed and then flushed and evacuatedwith nitrogen several times to remove oxygen. These flushes werefollowed by two rapid flushes with hydrogen to minimize residualnitrogen in the reactor. The reactor was equipped with amagnetically-coupled gas entrainment agitator which was rotated at about1000 rpm during the reaction. The reactor temperature was controlledeither by flowing a propylene glycol/water mixture from a recirculatingbath through an external coil, or by use of an external electrical bandheater. Hydrogen was continuously fed to the reactor during the courseof the run to maintain a specified pressure as hydrogen was consumed bythe reaction. Following the reaction, the reactor was cooled via theexternal cooling coil and vented. Product analysis was conducted by gaschromatography (GC) as described above using 1,2-dibromobenzene as theinternal standard added post reaction. Additional reaction conditionsand the corresponding reaction profiles showing conversion ofnepetalactones to dihydronepetalactones and key byproducts are providedbelow for the individual examples.

Example 1 (Comparative Example) Hydrogenation of Nepetalactone inUntreated Catmint Oil (CMO)

The reaction was carried out using ESCAT 142. The catalyst charge was 10wt % relative to the weight of CMO, the hydrogen pressure was 8.27 MPa,and the CMO concentration was 50 wt % in ethanol. The reaction wascarried out at 15° C.

TABLE 1 Hydrogenation of nepetalactone Puleganic NPL DHN Acid NeptalicAcid TOS Conv. Yield Yield Yield (h) (wt %) (wt %) (wt %) (wt %) 0.171.6 ** ** 5.9 0.50 8.5 97.3  3.11 5.9 1.00 18.2 98.3 1.8 5.9 1.5 38.498.1 1.9 6.2 2.0 47.6 98.1 1.9 5.9 ** too low to accurately measure.

Example 2 Solvent Distillation of Catmint Oil Using 21 Wt % Solvent

This example shows the effect of treating crude catmint oil by solventdistillation using ethanol on the rate of hydrogenation of nepetalactone(NPL) to dihydronepetalactone (DHN). Ethanol was added to crude catmintoil to about 21 wt %. The volatiles, including the ethanol, werestripped off using a single stage flash (no distillation column present)at 1.38 kPa (65° C.) for about 30 minutes, at which time no additionalvolatile components were observed coming overhead (i.e., no additionalcondensate (using a dry ice trap) was observed). Approximately 6 wt % ofthe original crude catmint oil was lost overhead in the distillation.The remaining material was used in a hydrogenation test performed asdescribed in Comparative Example 1. Table 2 shows the rate ofhydrogenating this treated oil as the NPL conversion as a function ofhydrogenation time or time on stream (TOS). After 2 hours ofhydrogenation, the conversion of the nepetalactone increased from 47.6%observed in Comparative Example 1 to 82.1% for the catmint oil subjectedto solvent distillation. No appreciable increase in the undesiredby-products, nepetalic acid and puleganic acid, were observed.

TABLE 2 Hydrogenation of nepetalactone Puleganic NPL DHN Acid NeptalicAcid TOS Conv. Yield Yield Yield (h) (wt %) (wt %) (wt %) (wt %) 0.1729.2 98.7 1.32 5.9 0.50 48.0 98.6 1.41 5.9 1.00 69.3 98.2 1.83 5.9 1.578.8 97.9 2.14 6.2 2.0 82.1 97.8 2.27 5.9

Example 3 Solvent Distillation of Catmint Oil at 50 Wt % Solvent

This example shows the effect of treating crude catmint oil by solventdistillation with ethanol on the rate of hydrogenation of nepetalactone(NPL) to dihydronepetalactone (DHN). Ethanol was added to crude catmintoil to about 50 wt %. This is substantially more than used in Example 2.The volatiles, including the ethanol, were stripped off using a singlestage flash at 7.58 kPa (65° C.) for about 30 minutes, at which time noadditional volatile components were observed coming overhead.Approximately 1 wt % of the original crude catmint oil was lost overheadin the distillation. The remaining material was used in a hydrogenationtest performed as described in Comparative Example 1. Table 3 shows therate of hydrogenating this treated oil as the NPL conversion as afunction of hydrogenation time or time on stream (TOS). After 2 hours ofhydrogenation, the conversion of the nepetalactone increased from 47.6%observed in Comparative Example 1 to 83.5% for the solvent distilledoil. This was done with no apparent increase in nepetalic acid or yieldloss to puleganic acid. The crude catmint oil had an initial sulfurcontent of 278 ppm; the content of the sulfur in the sample used forhydrogenation was 215 ppm.

TABLE 3 Hydrogenation of nepetalactone Puleganic NPL DHN Acid NeptalicAcid TOS Conv. Yield Yield Yield (h) (wt %) (wt %) (wt %) (wt %) 0.1720.3 96.8 3.7 6.1 0.50 42.4 99.5 0.6 6.1 1.00 60.6 97.8 2.4 6.1 1.5 76.397.6 2.6 5.8 2.0 83.5 97.4 2.8 6.2

Example 4 Steam Distillation of Catmint Oil, Followed by Distillationwith Isopropanol

This example shows the effect of treating crude catmint oil by steamdistillation, followed by distillation with isopropanol on the rate ofhydrogenation of nepetalactone (NPL) to DHN. Catmint oil (2400 grams;Lot 2003 from George Thacker Sons) and deionized water (1440 grams) werecombined in a 4 liter heated resin kettle outfitted with a shell andtube condenser and a dry ice cold finger. This resin kettle wasoutfitted with a vacuum control. Vacuum was controlled at a pressure of6.9 kPa while the kettle was heated using an electrical heating mantel.The temperature of the water and catmint oil was controlled at 39 to 45°C. Water and some of the catmint oil was stripped off, condensed usingthe shell and tube condenser and the cold finger and periodicallydrained from the condenser receiver. After about 7 hours, most of thewater was distilled off and a total of approximately 400 mL ofisopropanol was added to the catmint oil remaining in the resin kettle.The distillation was continued at about 6.9 kPa but the temperature ofthe catmint oil/isopropanol mixture was raised to 72 to 80° C. tofacilitate the distillation. The distillation was carried out for anadditional hour. For the last 10 to 15 minutes, the vacuum was adjustedto 752 Pa to help drive off any residual isopropanol. About 4.5 wt % ofthe initial charge of the oil was distilled off in this fashion. A totalof 7 distillations were performed in this fashion and the distilledcatmint oil obtained from the distillations was combined to give a totalof about 14.7 Kg of distilled catmint oil. A small portion was used in ahydrogenation test performed as described in Comparative Example 1.Table 4 shows the rate of hydrogenating this treated oil as the NPLconversion as a function of hydrogenation time or time on stream (TOS).After 1.75 hours of hydrogenation, the conversion of the nepetalactonewas 82.2%, which is substantially higher than the conversion atapproximately the same time in Example 1. This was done with no apparentincrease in nepetalic acid or yield loss to puleganic acid. The crudecatmint oil had an initial sulfur content of 278 ppm; the content of thesulfur in the sample used for hydrogenation was 205 ppm.

TABLE 4 Hydrogenation of nepetalactone Puleganic NPL DHN Acid NeptalicAcid TOS Conv. Yield Yield Yield (h) (wt %) (wt %) (wt %) (wt %) 0.1716.02 99.36 0.66 6.51 0.5 50.17 98.17 1.88 6.60 1 74.31 97.81 2.22 6.401.75 82.19 97.11 2.86 6.66 2.75 84.47 97.53 2.52 6.45

Examples 5-11 Hydrogenation of Nepetalactone

Examples 5 through 11 illustrate the hydrogenation of nepetalactone incatmint oil, where the crude catmint oil was treated as indicated.

The hydrogenation reactions were carried out using the catalyst ESCAT142. The catalyst charge was 10 wt % relative to the weight of thecatmint oil, the hydrogen pressure was 3.45 MPa, and the CMOconcentration was 50 wt % in ethanol. The reactions were carried out at25° C. The results are summarized in Table 5.

Example 5 is a Comparative Example for the hydrogenation rate ofnepetalactone in untreated catmint oil to dihydronepetalactone.

For Example 6, crude CMO was treated by solvent distillation withethanol. Ethanol was added to crude catmint oil to about 20 wt %. Thevolatiles, including the ethanol, were stripped off using a single stageflash at approximately 6.895 kPa (65° C.) for about 30 minutes, at whichtime no additional volatile components were observed coming overhead.Approximately 6 wt % of the original crude catmint oil was lost overheadin the distillation. The remaining material was used in a hydrogenationtest performed as described above.

For Example 7, crude CMO was treated by solvent distillation withethanol. Ethanol (100 grams) was added to 300 grams of crude catmintoil. The volatiles, including the ethanol, were stripped off using asingle stage flash at approximately 6.895 kPa to about 448 Pa (60° C.)for about 30 minutes, at which time no additional volatile componentswere, observed coming overhead. Approximately 4.5 grams of the originalcrude catmint oil was lost overhead in the distillation. The remainingmaterial was used in a hydrogenation test performed as described above.

For Example 8, crude CMO was treated by contacting it with a dilutehydrogen peroxide solution. A 30% solution of H₂O₂ (12 grams) wasdiluted with 108 grams of deionized water, and this solution was mixedwith 120 grams of crude CMO plus 8.5 grams of sodium chloride. Theresulting mixture was shaken vigorously in a separatory funnel. Theaqueous layer was removed, and the treated CMO was dried and filteredover 10 grams of 13X molecular sieves from Sigma-Aldrich (St. Louis,Mo.). This treatment yielded 108 grams of treated CMO. This material wasused in a hydrogenation test performed as described above.

For Example 9, crude CMO was treated by contacting it with a fixed bedof Borax (20 Mule Team® Borax). Glass wool was placed in the bottom of aglass column. Borax (50 grams) was loaded into this column. Crude CMO(142.4 grams) was drained through this column. This treatment yielded111 grams of treated CMO. This material was used in a hydrogenation testperformed as described above.

For Example 10, crude CMO was distilled under high vacuum of 15 to 25torr absolute. Crude CMO (19.05 kg) was charged to the distillation pot.This distillation was run under a vacuum of 25 to 15 torr. The pottemperature was increased from 120° C. to a final temperature of 147° C.Volatiles were collected from a dry ice cold finger. Seven fractions ofdistillate (8.34 kg) were collected. The third fraction was used in ahydrogenation test performed as described above. The crude catmint oilhad an initial sulfur content of 278 ppm; the content of the sulfur inthe third fraction used for hydrogenation was 49 ppm.

TABLE 5 Hydrogenation of nepetalactone Example 5: Example 6: Example 10:Comparative 20% ethanol Example 7: Example 9: High vacuum Untreateddistilled 50% ethanol Example 8: Borax treated (closed path) CMO CMOdistilled CMO H₂O₂ treated oil oil distilled oil >> NPL NPL NPL NPL NPLNPL TOS conversion conversion conversion conversion conversionconversion (h) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) 0.08 5.3 22.418.7 38.9 3.0 42.2 0.25 13.9 55.4 40.5 79.3 29.8 74.5 0.50 27.9 76.858.0 88.0 60.1 83.3 1.00 46.9 84.3 70.5 92.8 76.8 87.6 2.00 65.3 89.178.6 97.0 83.9 92.3 DHN 98.3 94.9 97.7 94.5 98.3 97.0 yield at 2 h (wt%)

For Example 11, crude CMO was contacted with an oxidizing agent.Hydrogen peroxide (30% solution; 50 grams) was mixed with 450 grams ofdeionized water. This mixture (500 grams) was combined with 5.1 grams ofsodium chloride and 500 grams of crude catmint oil having a sulfurcontent of approximately 592 ppm. This mixture was vigorously agitatedin a separatory funnel, allowed to settle, and then the aqueous phasewas separated from the organic phase by decantation. The organic phasewas dried over 13X mole sieves, and 467.4 grams of catmint oil wasrecovered. The sulfur content of this dried peroxide treated oil was 252ppm. This represents a 57% reduction in sulfur content of the oil. Asample of this treated oil was used in a hydrogenation test performed asdescribed above.

The results are shown in the Table 6. The H₂O₂ treated oil showedsubstantially increase conversion of the nepetalactone after 2 hours ofhydrogenation (83.7% versus 25.4% for the untreated oil).

TABLE 6 Hydrogenation of catmint oil NPL NPL Conv. Conv. TOS UntreatedH₂O₂-treated (h) (wt. %) (wt. %) 0.25 3.2 42.0 0.50 7.4 62.4 1.00 15.377.1 2.00 25.4 83.7

Example 12 Steam Distillation of Catmint Oil

This example shows the effect of treating crude catmint oil by steamdistillation on the rate of hydrogenation of nepetalactone (NPL) to DHN.Crude catmint oil (705 grams) plus 400 grams of water were loaded into a4 liter resin kettle outfitted with a condenser. The resin kettle washeated to its boiling point at atmospheric pressure for 4 hours. Some ofthe water and oil were distilled overhead and condensed. Water (136grams) and 30 grams of organics (by phase weight) were collected in thedistillate receiver. The remaining catmint oil in the resin kettle wasdecanted from the water phase and used in a hydrogenation test. Table 6shows the rate of hydrogenating this treated oil as the NPL conversionas a function of hydrogenation time or time on stream (TOS). After 2hours of hydrogenation, the conversion of the nepetalactone was 89.2%for this steam distilled oil. The data from Table 7 can be compared tothe data from Table 8 in Example 13 for untreated catmint oil.

Hydrogenation Conditions:

The reaction was carried out using the catalyst ESCAT 142. The catalystcharge was 10 wt % relative to the weight of the catmint oil, thehydrogen pressure was 0.21 MPa, and the CMO concentration was 10 wt % inhexane. The reaction was carried out at 25° C.

TABLE 7 Hydrogenation of nepetalactone Puleganic Neptalic NPL DHN AcidAcid Conv. Yield Yield Yield TOS (h) (wt %) (wt %) (wt %) (wt %) 0.1746.5 ** ** 10.2 0.50 80.7 ~100 ~0 9.7 1.00 86.3 ~100 ~0 9.0 1.5 87.5~100 ~0 9.8 2.0 89.2 ~100 ~0 9.5 ** too low to accurately measure.

Example 13 (Comparative Example) Hydrogenation of Nepetalactone

Crude catmint oil was hydrogenated under the conditions described inExample 12. For this untreated oil, there was only a 64.8% conversion ofthe NPL after 2 hours.

TABLE 8 Hydrogenation of nepetalactone Puleganic NPL DHN Acid NeptalicAcid TOS Conv. Yield Yield Yield (h) (wt %) (wt %) (wt %) (wt %) 0.177.3 84.9 ** 1.11 0.50 23.5 94.5 4.9 1.11 1.00 43.4 95.6 4.0 1.13 1.556.3 95.4 4.2 1.13 2.0 64.8 95.7 4.0 1.16

Where a range of numerical values is recited herein, the range includesthe endpoints thereof and all the individual integers and fractionswithin the range, and also includes each of the narrower ranges thereinformed by all the various possible combinations of those endpoints andinternal integers and fractions to form subgroups of the larger group ofvalues within the stated range to the same extent as if each of thosenarrower ranges was explicitly recited. Where a range of numericalvalues is stated herein as being greater than a stated value, the rangeis nevertheless finite and is bounded on its upper end by a value thatis operable within the context of the invention as described herein.Where a range of numerical values is stated herein as being less than astated value, the range is nevertheless bounded on its lower end by anon-zero value.

In this specification, unless explicitly stated otherwise or indicatedto the contrary by the context of usage, amounts, sizes, ranges,formulations, parameters, and other quantities and characteristicsrecited herein, particularly when modified by the term “about”, may butneed not be exact, and may also be approximate and/or larger or smaller(as desired) than stated, reflecting tolerances, conversion factors,rounding off, measurement error and the like, as well as the inclusionwithin a stated value of those values outside it that have, within thecontext of this invention, functional and/or operable equivalence to thestated value.

In this specification, unless explicitly stated otherwise or indicatedto the contrary by the context of usage, where an embodiment of thesubject matter hereof is stated or described as comprising, including,containing, having, being composed of or being constituted by or ofcertain features or elements, one or more features or elements inaddition to those explicitly stated or described may be present in theembodiment. An alternative embodiment of the subject matter hereof,however, may be stated or described as consisting essentially of certainfeatures or elements, in which embodiment features or elements thatwould materially alter the principle of operation or the distinguishingcharacteristics of the embodiment are not present therein. A furtheralternative embodiment of the subject matter hereof may be stated ordescribed as consisting of certain features or elements, in whichembodiment, or in insubstantial variations thereof, only the features orelements specifically stated or described are present.

What is claimed is:
 1. A process for preparing hydrogenated catmint oil,comprising: (a) contacting a beginning amount of crude catmint oil withNa₂B₄O₇.10H₂O; (b) distilling the beginning amount of crude catmint oilto produce (i) a distillate fraction comprising volatile componentsdriven off from the crude catmint oil, wherein the weight of thedistillate fraction comprises about 2% to about 20% of the weight of thebeginning amount of crude catmint oil, and (ii) a pot fraction; (c)contacting the pot fraction produced in step (b) with hydrogen and ahydrogenation catalyst to produce hydrogenated catmint oil; and (d)optionally, recovering the hydrogenated catmint oil of step (c).
 2. Theprocess of claim 1 wherein the weight of the distillate fractioncomprises about 5% to about 10% of the weight of the beginning amount ofcrude catmint oil.
 3. The process of claim 1 wherein the step ofdistilling (a) comprises a step of (i) vacuum distilling, (ii) steamdistilling, (iii) solvent distilling, or (iv) steam distilling followedby solvent distilling.
 4. The process of claim 3 which comprises a stepof solvent distilling, or of steam distilling followed by solventdistilling, and wherein, at the beginning of solvent distilling, theweight of the solvent comprises about 5% to about 60% of the combinedweight of catmint oil plus solvent.
 5. The process of claim 4 wherein,at the beginning of solvent distilling, the weight of the solventcomprises about 10% to about 25% of the combined weight of catmint oilplus solvent.
 6. The process of claim 3 which comprises a step ofsolvent distilling, or of steam distilling followed by solventdistilling, and wherein a solvent comprises a C₁ to C₅ straight-chain orbranched alcohol.
 7. The process of claim 6 wherein the alcohol isselected from the group consisting of methanol, ethanol, isopropanol andn-propanol.
 8. The process of claim 3 wherein steam distilling, solventdistilling, or steam distilling followed by solvent distilling, isperformed under vacuum.
 9. The process of claim 1 wherein the potfraction is contacted with hydrogen and a hydrogenation catalyst at atemperature of about −10° C. to about 200° C.
 10. The process of claim 1wherein the pot fraction is contacted with hydrogen and a hydrogenationcatalyst at a temperature of about 25° C. to about 250° C.
 11. Theprocess of claim 1 wherein the pot fraction is contacted with hydrogenat a hydrogen pressure of about 0.1 MPa to about 20.7 MPa.
 12. Theprocess of claim 1 wherein the pot fraction is contacted with hydrogenand a hydrogenation catalyst comprising a catalytic metal selected fromelements from the group consisting of iron, ruthenium, rhenium, copper,osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, alloys orcompounds thereof; and combinations thereof.
 13. A process for preparinghydrogenated catmint oil comprising: (a) contacting crude catmint oilwith Na₂B₄O₇.10H₂O to produce a first treated catmint oil; (b)separating the first treated catmint oil from the oxidizing agent toproduce a second treated catmint oil; (c) contacting the second treatedcatmint oil with hydrogen and a hydrogenation catalyst to producehydrogenated catmint oil; and (d) optionally recovering the hydrogenatedcatmint oil.
 14. The process of claim 13 wherein the second treatedcatmint oil is contacted with hydrogen and a hydrogenation catalyst at atemperature of about −10° C. to about 200° C.
 15. The process of claim13 wherein the second treated catmint oil is contacted with hydrogen anda hydrogenation catalyst at a temperature of about 25° C. to about 250°C.
 16. The process of claim 13 wherein the second treated catmint oil iscontacted with hydrogen at a hydrogen pressure of about 0.1 MPa to about20.7 MPa.
 17. The process of claim 13 wherein the second treated catmintoil is contacted with hydrogen and a hydrogenation catalyst comprising acatalytic metal selected from elements from the group consisting ofiron, ruthenium, rhenium, copper, osmium, cobalt, rhodium, iridium,nickel, palladium, platinum, alloys or compounds thereof; andcombinations thereof.